1. Field of the Invention
This invention relates to photographic elements, and, more particularly, it is concerned with X-ray sensitive photographic elements of improved antistatic properties for use in modern rapid exposure and high speed transport medical X-ray equipment.
2. DESCRIPTION OF THE PRIOR ART
It has been known in general for a long time that the motivating, handling, winding, unwinding and the like operations, when applied to webbed materials, may encounter problems of friction, static, and the like. This is particularly true in handling photographic elements or films having one or more sensitized layers on one side of a photographic support and usually a backing layer on the opposite surface of said support. These problems are further heightened in the case of medical X-ray film by the fact that:
(1) X-ray film has two separate and independent sensitized layers on opposing surfaces of said support, and by the fact that; PA1 (2) Recent innovations in medical X-ray processing equipment, which have been characterized by the replacement of conventional, single sheet exposing equipment with new, rapid exposure and film transport equipment, have increased processing difficulties. Such difficulties, for example, that can be caused by the new medical X-ray processing equipment, can be static discharge on the resulting element or film product, which discharge is recorded as black spots or streaks and arises as a result of rapid transport between rubber rollers or the like. Another difficulty results from jamming of the X-ray film in such equipment if the sheets do not or will not slide smoothly from the storage area to the exposure area and then to another storage area prior to processing. As examples of such new equipment presently commercially available utilizing this new technique of rapid transport exposure are those apparatus or machines marketed by Elema-Schonander (Model DST-843-2), duPont (duPont Cronex Daylight Chest Changer Model 1000), and Picker Corporation (Picker Chest Changer, Catalog No. 750-551-1).
Previous practice for resolving or at least minimizing such problems has been the application of various additive materials such as lubricating coatings, antistatic coatings, or use of other expedients such as interleaving, etc., for facilitating handling and other operations as applied to the photographic element or film.
By means of the present invention, however, improvements in conventional photographic elements or films such as color, black-and-white, and medical X-ray film, and in their conventional methods of manufacture, are now made available which permit broadened use of such photographic elements and, in particular, provide improved X-ray films for application in the new exposure-equipment now available to the art.
The prior art is represented by such U.S. Pat. Nos. as 3,933,516; 4,013,696 and Re-29,255.
Accordingly, it is an object of this invention to provide an improved photographic element which is characterized by a protective surface layer of substantially improved antistatic properties for use in modern rapid exposure and high speed transport medical X-ray equipment.
Another object of this invention is to provide such a layer which exhibits excellent coating uniformity of the surface material, when applied by multiple slide hopper metering techniques.
Still another object is to provide a gelatin based protective surface layer of an X-ray film which contains a highly branched perfluoronated fluorocarbon in a composition range which is particularly effective in reducing static defects during processing while showing good film sensitometric response.